JP2011224445A - Apparatus for treating wastewater containing ammonium salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for treating wastewater containing ammonium salt that can efficiently treat wastewater containing ammonium salt by increasing electric conductivity in a cation concentration chamber, and reducing power consumption of an electrodialyzer in the apparatus for treating wastewater containing ammonium salt by the electrodialyzer.SOLUTION: The apparatus for treating wastewater containing ammonium salt is adapted to supply wastewater containing ammonium salt into a desalting chamber 18 of the electrodialyzer 10, to take out acid-containing water from an anion concentration chamber 17 and to take out ammonia water from a cation concentration chamber 19. The apparatus includes return lines 40, 44 returning ammonia water taken out of the cation concentration chamber 19, to the cation concentration chamber, and a carbon dioxide blow-in tank 41 blowing carbon dioxide into ammonia water.

Description

  The present invention relates to a treatment apparatus for ammonium salt-containing wastewater for treating wastewater containing ammonium salt such as ammonium nitrate, and more particularly to a treatment apparatus for ammonium salt-containing wastewater using an electrodialyzer. In detail, it is related with the processing apparatus of the ammonium salt containing waste water suitable for the processing of the ammonium salt containing waste water from the refinement | purification process of a metal oxide.

  In order to increase the purity of yttrium oxide used as a raw material for phosphors, low-purity yttrium oxide ore is dissolved in acid, and then precipitated and precipitated as hydroxide or carbonate. It has been broken. From this process, a large amount of waste water containing acid solution and cations (ammonium ions when precipitating as carbonate), which is a by-product when precipitating and precipitating, is drained, and the waste water contains a lot of nitrogen components. Need to be processed.

  Also from the step of taking out the cerium compound and the rare earth element compound from the monazite, the ammonium nitrate-containing waste water is discharged and needs to be treated in the same manner.

  In JP-A-7-163845, ammonium nitrate-containing wastewater is supplied to a desalting chamber of an electrodialyzer, ammonium ions are moved from the desalting chamber to an anion concentration chamber, taken out as an ammonia solution, and nitrate ions are cationized from the desalting chamber. It is described that it is moved to a concentrating chamber and taken out as nitric acid.

JP 7-163845 A

Since NH ₄ ⁺ moved from the desalting chamber of the electrodialyzer to the cation concentration chamber becomes NH ₃ having a low degree of ionization, the conductivity of the cation concentration chamber is lowered. This causes an increase in voltage and increases the power consumption of the electrodialysis apparatus.

  The present invention relates to an ammonium salt-containing wastewater treatment device for treating ammonium salt-containing wastewater with an electrodialyzer, which increases the conductivity in the cation concentration chamber, reduces the power consumption of the electrodialyzer, and efficiently contains ammonium salt. An object of the present invention is to provide an ammonium salt-containing wastewater treatment apparatus capable of treating wastewater.

  An apparatus for treating ammonium salt-containing wastewater according to claim 1, wherein an anion exchange membrane and a cation exchange membrane are disposed between an anode and a cathode to form a desalting chamber, an anion concentration chamber, and a cation concentration chamber. An apparatus for treating ammonium salt-containing wastewater using an apparatus, wherein ammonium salt-containing wastewater is supplied to the desalting chamber, acid-containing water is taken out from the anion concentration chamber, and ammonia water is taken out from the cation concentration chamber The apparatus for treating ammonium salt-containing wastewater, comprising: a return line for returning the ammonia water taken out from the cation concentration chamber to the cation concentration chamber; and a carbon dioxide gas blowing means for blowing carbon dioxide into the ammonia water. To do.

  The treatment apparatus for waste water containing ammonium salt according to claim 2 is characterized in that, in claim 1, the carbon dioxide blowing means is provided in the middle of the return line.

  According to a third aspect of the present invention, there is provided a treatment apparatus for wastewater containing ammonium salt, comprising the reverse osmosis membrane device for performing reverse osmosis treatment on the demineralized water taken out from the demineralization chamber. .

  In the present invention, ammonium salt-containing wastewater is supplied to the desalting chamber of the electrodialyzer, acid ions are moved from the desalting chamber to the anion concentration chamber, and ammonium ions are transferred from the desalting chamber to the cation concentration chamber (ammonium ion concentration chamber). Move to. The ammonia-containing water taken out from the cation concentration chamber is returned to the cation concentration chamber and circulated, and carbon dioxide gas is blown into the ammonia-containing water. As a result, ammonia in the ammonia-containing water reacts with carbon dioxide gas to become ammonium carbonate, the degree of ionization (degree of dissociation) increases, and the conductivity of water in the ammonium ion concentration chamber of the electrodialyzer increases. For this reason, the electrical conductivity of the cation concentration chamber of the electrodialyzer increases, and the power consumption of the electrodialyzer decreases.

  When carbon dioxide gas is blown into the cation concentration chamber of the electrodialyzer, gas accumulation may occur in the cation concentration chamber, and it is preferable that the carbon dioxide gas be blown into the return line because the space in the cation concentration chamber is small.

  Demineralized water with a low ammonium salt concentration taken out from the electrodialyzer can be treated to a concentration below the discharge standard by subjecting it to desalination treatment with a reverse osmosis membrane device (RO device) as necessary.

It is a flowchart which shows an example of this invention apparatus.

  Hereinafter, the present invention will be described in detail with reference to FIG.

  The present invention treats ammonium salt-containing wastewater using an electrodialyzer. Examples of the ammonium salt-containing wastewater include, but are not limited to, ammonium nitrate-containing wastewater such as wastewater from the purification process of yttrium oxide and wastewater from the step of taking out cerium compounds and rare earth compounds from monazite. For example, the present invention can be applied to a process of separating ammonium sulfate by-produced from a nylon raw material production process into sulfuric acid and ammonia. It can also be applied to the treatment of wastewater containing ammonium chloride, ammonium fluoride and the like.

  When the ammonium nitrate-containing wastewater is treated, the ammonium nitrate concentration in the ammonium nitrate-containing wastewater is preferably about 10 to 30 wt%, particularly about 15 to 25 wt%. This ammonium nitrate-containing wastewater may contain carbonate ions and the like.

  The raw water is preferably subjected to centrifugal separation or membrane filtration (for example, UF membrane filtration) in advance to remove fine particles such as metal oxide and metal carbonate.

  FIG. 1 shows an example of a flow for treating ammonium nitrate-containing waste water. In the electrodialysis apparatus 10, a cation exchange membrane 13 and an anion exchange membrane 14 are disposed between an anode 11 and a cathode 12. In this embodiment, a bipolar membrane 15 is further disposed. As shown in the figure, the bipolar membrane is formed by laminating an anion exchange membrane and a cation exchange membrane, and is arranged such that the anion exchange membrane surface faces the cathode 12 and the cation exchange membrane surface faces the anode 11. ing. A cation exchange membrane 13 is disposed closest to the anode 11, and an anode chamber 16 is formed between the anode 11 and the cation exchange membrane 13. An anion exchange membrane 14 is disposed on the most cathode 12 side, and a cathode chamber 20 is formed between the cathode 12 and the anion exchange membrane 14.

  From the anode chamber 16 side toward the cathode chamber 20 side, the cation exchange membrane 13, the nitrate ion concentration chamber 17 as the anion concentration chamber, the anion exchange membrane 14, the desalting chamber 18, the cation exchange membrane 13, and the ammonium ion as the cation concentration chamber A concentration chamber 19, a bipolar membrane 15, a nitrate ion concentration chamber 17, an anion exchange membrane 14, a desalting chamber 18, a cation exchange membrane 13, an ammonium ion concentration chamber 19, and an anion exchange membrane 14 are arranged. As described in detail later, the desalting chamber 18 is preferably mixed and filled with a cation exchange resin and an anion exchange resin.

  The raw water (ammonium nitrate-containing wastewater) is supplied from the raw water line 1 to the desalting chamber 18, introduced into the desalting water tank 3 through the extraction line 2, and passed through the pump 4, the return line 5 and the line 1 to the desalting chamber 18. Circulated. Note that a desalted water extraction line 6 branches from the line 5.

  Nitric acid ions that pass through the anion exchange membrane 14 and move from the desalting chamber 18 to the nitrate ion concentrating chamber 17 are introduced into the nitrate ion concentrating chamber 17 from the nitric acid line 30 into the nitric acid tank 31, and the pump 32. , And returned to the nitrate ion concentration chamber 17 via the line 33. A nitric acid extraction line 34 is branched from the line 33.

  In this embodiment, ammonium ions permeate the cation exchange membrane 13 and move from the desalting chamber 18 to the ammonium ion concentrating chamber 19 to produce ammonia and ammonium hydrogen carbonate-containing water. The contained water is introduced into the carbon dioxide gas blowing tank 41 from the line 40, and carbon dioxide gas is blown from the diffuser pipe 42. As a result, ammonia becomes ammonium bicarbonate (ammonium bicarbonate). This ammonium bicarbonate-containing water is returned to the ammonium ion concentration chamber 19 via the pump 43 and the line 44. A line 44 for branching out ammonium bicarbonate-containing water branches from the line 44. The amount of carbon dioxide blown is suitably such that the pH in the carbon dioxide blown tank is neutral, for example, about 6-8.

  When the ammonium salt-containing wastewater treatment apparatus 10 configured as described above is used to treat ammonium nitrate-containing wastewater, it is preferable that pure water is filled in the concentration chambers 17 and 19 and the tanks 31 and 41 at the start of operation. . Moreover, it is preferable that raw water is stretched over the desalting chamber 18 and the desalted water tank 3.

It is preferable to pass a Na ₂ SO ₄ solution that hardly causes an electrode reaction through the anode chamber 16 and the cathode chamber 20.

The raw water in the desalted water tank 3 is circulated in the order of the pump 4, lines 5, 1, the desalting chamber 18 and the line 2, and the water in the nitrate ion concentrating chamber is circulated in the order of the line 30, the tank 31, the pump 32 and the line 33. Let In addition, the water in the ammonium ion concentrating chamber is circulated in the order of the line 40, the carbon dioxide blowing tank 41, the pump 43, and the line 44, and carbon dioxide is blown into the carbon dioxide blowing tank 41 from the diffuser tube 42, so that NH ₄ OH component is NH. ₄ HCO ₃ The nitrate ions in the raw water pass through the anion exchange membrane 14 and move to the nitrate ion concentration chamber 17, and the ammonium ions pass through the cation exchange membrane 13 and move to the ammonium ion concentration chamber 19. Thereby, the nitrate ion concentration and the ammonium ion concentration in the raw water passing through the desalting chamber 18 are gradually decreased. Moreover, the nitric acid concentration in the nitric acid tank 31 gradually increases, and the ammonium bicarbonate ion concentration in the carbon dioxide gas blowing tank 41 also gradually increases.

As described above, since the liquid in which the NH ₄ OH component has become NH ₄ HCO ₃ is circulated through the carbon dioxide gas blowing tank 41 into the ammonium ion concentrating chamber 19, the conductivity in the ammonium ion concentrating chamber 19 is increased. The power consumption of the electrodialyzer is reduced.

  Note that when batch circulation treatment is performed in this manner, the salt concentration in the desalted water is lowered, so that the resistance in the desalting chamber 18 is increased and the power consumption is increased. Therefore, it is desirable to fill ion exchange resin in the desalting chamber 18 to reduce the electrical resistance in the desalting chamber 18.

  The desalting chamber 18 is preferably filled with both a cation exchange resin and an anion exchange resin. The ratio of the cation exchange resin to the total amount of the cation exchange resin and the anion exchange resin is preferably 90% or less, particularly preferably 40% or less. A smaller amount of cation exchange resin is preferable because current flows easily.

  When a predetermined amount or more, for example, 90% of ions are collected by electrodialysis, the desalting step is terminated. The timing for ending the desalting step can be determined by measuring the conductivity of the desalted water.

  By sufficiently desalting with the electrodialyzer 10, the ammonium nitrate concentration in the desalted water is reduced to about 0.1 mol / L or less. If the ammonium nitrate concentration is lowered so far, this desalted water can be treated with the RO membrane. Therefore, the demineralized water in the demineralized water tank 3 is supplied from the line 6 to the RO device and subjected to RO treatment.

  RO treated water from which ammonium nitrate is further removed by 90% or more by RO treatment is discharged to sewage / drainage treatment facilities. Concentrated water is treated separately or returned to the treatment of the electrodialyzer 10.

When the HNO ₃ solution and ammonium bicarbonate solution in the tanks 31 and 41 are reused, since the ion recovery rate by electrodialysis is 90%, a concentrated nitric acid solution or ammonium bicarbonate solution is used for the amount less than the specified concentration. Add to adjust concentration. When the concentration is grasped online, it is preferable to measure the concentration using a conductivity meter, a specific gravity meter, etc., and adjust it to a prescribed solution concentration.

  INDUSTRIAL APPLICABILITY The present invention is suitable for use in applications where wastewater from a metal oxide purification process is treated and the recovered ammonium bicarbonate solution and an acid solution such as nitric acid are reused in the purification process. In this case, in addition to ammonium ions, metal ions move from the desalting chamber 18 to the ammonium ion concentration chamber 19, so there is a possibility that the metal ions are concentrated in the recovered ammonium bicarbonate solution. Therefore, it is preferable to reuse the recovered ammonium bicarbonate solution after contacting the chelate resin to remove metal ions.

  In the above embodiment, a bipolar membrane is used as the electrodialyzer 10, but only a cation exchange membrane and an anion exchange membrane are alternately provided between the anode and the cathode as disclosed in JP-A-2003-305475. An electrodialyzer arranged in the above may be used.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
According to the flow shown in FIG. 1, a desalting treatment of an ammonium nitrate solution having a concentration of 1 mol / L was performed.

The anion exchange membrane “Neocepta AHA” manufactured by Astom Co., Ltd. was used as the anion exchange membrane of the electrodialysis apparatus, and the cation exchange membrane “Neocepta CMB” manufactured by Astom Co., Ltd. was used as the cation exchange membrane. As the bipolar membrane, “BP-1E” manufactured by Astom Co., Ltd. was used. The film area was 0.46 dm ² . A Pt-coated Ti electrode manufactured by Permerec was used for the anode, and a stainless steel 304 electrode was used for the cathode.

A DC power supply (Kikusui Electronics Co., Ltd. compact variable switching power supply PAK35-10A) was used as the electrodialysis apparatus, and energization was performed at a constant current setting of 2.5A. Current density is 5.4A / dm ^2.

Prior to the start of operation of the electrodialyzer, the desalting chamber and the raw water circulation line were filled with a total of 500 mL of ammonium nitrate solution. The nitrate ion concentration chamber 17 and its circulation line were filled with 150 mL of pure water. The ammonium ion concentration chamber 19 and its circulation line were filled with 400 mL of pure water. A Na ₂ SO ₄ solution (concentration: 5000 mg / L) was circulated through the anode chamber 16 and the cathode chamber 20, respectively.

  The raw water circulating water amount in line 5 is set to 500 mL / min, the nitric acid solution circulating water amount in line 33 is set to 250 mL / min, and the ammonium bicarbonate solution circulating water amount in line 44 is set to 250 mL / min. Carbon dioxide gas was blown so that became a neutral region (6-8).

  The operation was continued for about 20 hours until the ammonium nitrate concentration in the desalted water tank 3 was 0.1 mol / L or less. Table 1 shows the energization voltage of the electrodialyzer until 12 hours after the start of operation.

[Example 2]
In Example 1, assuming that the ammonia concentration other than ammonium nitrate in the water taken out from the ammonium ion concentrating chamber 19 via the line 40 is 1 mol / L, the carbonic acid is preliminarily set to 1 mol / L with HCO ₃ ^−. The operation was started after carbon dioxide gas was blown into pure water in the gas blowing tank 41. Other conditions were the same as in Example 1. Table 1 shows the energization voltage of the electrodialyzer until 12 hours after the start of operation.

[Comparative Example 1]
The operation was performed under the same conditions as in Example 1 except that carbon dioxide was not blown into the carbon dioxide blowing tank 41. Other conditions were the same as in Example 1. Table 1 shows the energization voltage of the electrodialyzer until 12 hours after the start of operation.

  As shown in Table 1, in Example 1, the voltage was lower than that in Comparative Example 1 after 3 hours or more had elapsed from the start of operation. In Example 2, since carbonic acid was blown in advance, the voltage was lower than that in Example 1 and Comparative Example 1 immediately after the start of operation.

  On the other hand, in Comparative Example 1, the energization voltage was the same as that in Example 1 until 2 hours passed from the start of operation, but thereafter, the energization voltage gradually increased, and the voltage difference from Example 1 Gradually increased. In Comparative Example 1, the energization voltage gradually decreases as ammonium ions move to the concentration chamber 19 until 2 hours have elapsed since the start of operation.

3 Raw Water Tank 10 Electrodialyzer 13 Cation Exchange Membrane 14 Anion Exchange Membrane 41 Carbon Dioxide Blowing Tank 42 Aeration Tube

Claims (3)

An ammonium salt-containing wastewater treatment apparatus using an electrodialysis apparatus in which a desalination chamber, an anion concentration chamber, and a cation concentration chamber are formed by disposing an anion exchange membrane and a cation exchange membrane between an anode and a cathode. And
In the apparatus for treating ammonium salt-containing wastewater, wastewater containing ammonium salt is supplied to the desalting chamber, acid-containing water is taken out from the anion concentration chamber, and ammonia water is taken out from the cation concentration chamber.
A return line for returning the aqueous ammonia extracted from the cation concentration chamber to the cation concentration chamber;
An apparatus for treating wastewater containing ammonium salt, comprising carbon dioxide blowing means for blowing carbon dioxide into ammonia water.   The apparatus for treating wastewater containing ammonium salt according to claim 1, wherein the carbon dioxide gas blowing means is provided in the middle of the return line.   The apparatus for treating wastewater containing ammonium salt according to claim 1 or 2, further comprising a reverse osmosis membrane device for reverse osmosis treatment of the desalted water taken out from the desalting chamber.

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